the NSLINKMODULE_OPTION_PRIVATE option was added back then to prevent Pd from crashing when loading a library with a global symbol defined, which clashes with a definition from another, already loaded library.
...aha: I now see that this was added back about 2 years ago...however, I think this is/was a solution to a problem that no longer exists on OSX...that is, if we build externals without the "-flat_namespace", then they will automatically be built as "-twolevel_namespace", and this will prevent the library definition clashes...
btw: there is an option called NSLINKMODULE_OPTION_RETURN_ON_ERROR that returns if a linking error occurs. maybe it would be wise to use this as a replacement.
lg martin